1. Field of the Invention
The present invention relates in general to an electronically operated apparatus using an integrated-circuit memory in the form of an IC card, and more particularly to an arrangement for electrical connection between a ground terminal of an IC card and the main frame of the electronic apparatus. Further, the invention is concerned with such an electronic apparatus that uses as a control unit a central processing unit which requires an acknowledge signal upon data transfer to and from the IC card.
2. Discussion of the Prior Art
There is known an electronic apparatus such as a printer or a personal computer which uses an integrated-circuit card or IC card as an external memory device. Such an electronic apparatus includes (a) a main frame, (b) a card receptacle including a card connector to which an IC card is connectable and which has a reference potential terminal for connection to a ground terminal of the IC card, (c) a control portion capable of sending and receiving signals to and from the IC card through the card connector and having a reference potential equal to that of the main frame. The IC card, which includes as a major component a semiconductor IC memory element, is standardized in Japan by the Japanese Electronic Industry Development Association (JEIDA). The JEIDA Standard requires the IC card to be inserted in the card receptacle provided on an electronic apparatus such that the terminals of the IC card are connected to the respective terminals provided in the card connector of the receptacle, to permit data transfer between the IC card and the apparatus. Further, the above Standard requires the ground terminal of the IC card to be connected to the reference potential terminal of the card connector. Generally, the reference potential terminal of the card connector is connected to a part of the control portion of the apparatus which has a reference potential, that is, connected to a signal ground (apparatus SG) of the control portion, so that the reference potential of the IC card is equal to that of the apparatus SG.
Usually, the ground terminal of the IC card is connected to a signal ground (card SG) of the substrate of the IC card. IC cards produced by some manufacturers have a covering frame which is connected to the card SG via springs or other conductive members. In this case, the covering frame serves as a card frame ground (card FG), which is connected to the apparatus SG. According to this arrangement, the apparatus SG may be exposed to static electricity generated by the card FG, and the control portion of the apparatus tends to suffer from malfunctioning due to the static electricity. Also, noises produced by the control portion may radiate from the card FG which functions as an antenna. Thus, the IC card having the card FG has an adverse influence on the noise-free operation of the electronic apparatus.
On the other hand, the control portion of some electronic apparatus incorporates a central processing unit (CPU) as a control unit which requires an acknowledge signal indicative of completion of a data transfer to and from an IC card. A 16-bit CPU 6800 available from Motorola Semiconductor, U.S.A., is an example of such control CPU. When an electronic apparatus incorporating such control CPU uses an IC card as an optional memory, the control CPU should be supplied with the above-indicated acknowledge signal when the data transfer takes place between the control CPU and the IC card.
However, some IC cards such as those in the process of standardization by the JEIDA do not have an output terminal for the acknowledge signal indicated above, and cannot be used for an electronic apparatus which uses a control CPU that requires the acknowledge signal.